Position sensors are included in various systems, devices, and environments. Moreover, various types of position sensors have been developed for inclusion into these various systems, devices, and environments. One particular genre of position sensor that has been developed is the transformer position sensor. A transformer position sensor typically includes a primary or excitation coil, a secondary or output coil, a movable magnetically permeable core, and five wires to interconnect the sensor to external excitation and processing circuitry. When the excitation coil is electrically excited with an excitation signal, the output coil is inductively coupled to the excitation coil and supplies an output signal that is based on the position of the movable core. One particularly popular type of transformer position sensor is the variable differential transformer position sensor, which includes linear variable differential transformers (LVDTs) and rotary variable differential transformers (RVDTs). A variable differential transformer position sensor also includes an excitation coil, an output coil, and a movable magnetically permeable core. However, with variable differential transformer position sensors either the excitation coil or the output coil is configured as a pair of differentially wound coils that are electrically coupled in series.
The above-described transformer position sensors have been used for several years in relatively harsh aircraft environments where position sensing is need, such as within the gas turbine engine envelope. Thus, reliability issues have driven some gas turbine engine manufacturers to use these transformer position sensors, namely LVDTs, to replace the switches that are currently used to supply two discrete (e.g., open or closed) valve position signals. Although presently known transformer position sensors are generally safe, reliable, and robust, ever increasing demand for relatively lower cost and weight, and the opportunity to simplify aircraft architecture have driven the need to create an alternative to a 5-wire transformer position sensor to detect the position of a two-position valve. The present invention addresses at least this need.